Yes, that's right. 343 is going to run a beta test later this month for a big update that they hope will solve the game's matchmaking woes. Xbox One users in North America are eligible to sign up, test out "changes to the matchmaking experience and party system" and report any bugs they find.

In other words, we are now in the realm of beta testing games that are already out.

While the announcement post for the update never explicitly mentions problems with the game, it's not hard to read between the lines, especially when it comes to this bit:

Q: Why are you testing the content update in the Xbox One Preview program? Don't you have internal playtesting for the very same purpose?

A: In recent weeks, 343 Industries has been conducting extensive internal testing of the upcoming content update. However, given the scale of the update, which includes changes to the Halo: The Master Chief Collection matchmaking experience and party system, we are opening it up to members of the Xbox One Preview program to provide additional testing in an "at home" environment to ensure the official release is the best possible experience for players.